I don't think they are bantams. Where did you buy the birds and do you know what hatchery they came from or are they just some "chickens" someone hatched out of some of their "chickens".

The first one is a cockerel. The rest (for now) look like pullets.

Also there is no such breed as "Red Burn" or at least that I have ever heard of. It is possible that someone tried to make a Sex-linked bird which may attribute for the different coloring between the young roo and the girls, or they could just be different breeds.

I agree with the 1st being a roo and the rest look like pullets. They don't look like any breed I've seen here in america yet. They could just be mutts. Nice looking chicks. Judging by the size of the roo in your hand they look like standard size chicks. They look like at least 2 different breeds because the roo's feet are black. How old are they?